1. Technical Field
The present disclosure relates to an angle detecting module and an angle detecting method for a permanent-magnet synchronous motor and more particularly, relates to an angle detecting module and an angle detecting method for a permanent-magnet synchronous motor using hall sensors to convert a magnetic flux of the motor rotor to a rotor angle and method thereof.
2. Description of Related Art
A permanent-magnet synchronous motor has the features of energy saving, compact size and easy to control which meet the requirements of the industry, and thus has been gradually accepted by the market and is widely used on industrial applications. In the operation of the permanent-magnet synchronous motor, rotor angle or position information is required, such that a driver can generate proper switching signals for power supply to produce corresponding voltage in driving control. Conventionally, when commutation control of motor is performed, a high precision encoder is necessary to detect the rotor angle as a feedback signal. However, the encoder is usually expensive, structure vulnerable, complicated in wirings, and is easily interfered by electromagnetic noises in practical applications. Except for encoder, some low-cost sensors such as hall sensor can be utilized to provide the basis of rotor commutation and rotational speed calculation for a permanent-magnet synchronous motor. The using of hall sensor can not only achieve the requirements of commutation and speed control, but also simplify the motor control and reduce the cost.
Referring to a conventional application example shown in FIG. 1, a digital hall component with electrical 60 degrees in resolution is utilized to obtain rotor position roughly while motor rotates. Because six-step trapezoidal phase current control is adopted in that, the inherent larger torque ripple makes it difficult to satisfy the precision requirement of high-end application. Hence, in some known technique, approximate sine wave signal is generated to increase rotor angle resolution by using a linear hall component with similar cost instead.
Referring to a typical application example using linear hall components shown in FIG. 2, two linear hall components with 90 degrees phase shift are disposed. From their output signals, motor rotor position information can be extracted dealing with their trigonometric relationship. While the imperfect sine waveform of the output hall signals are, larger deviation between the calculated rotor angle and the actual one still exists.
Referring to a conventional application example using linear hall components shown in FIG. 3, the output signals of the three linear hall components are used as three-phase sine wave current commands in current control loop and the subsequent motor speed and direction control. In this case, although torque ripple is smaller than that in the aforementioned case in FIG. 1 because of a sine wave control method used therein, the wave form of the output signal of the linear hall component is still imperfect, and hence results in poor performance on control precision.
From the above application examples, with considerations of cost, reliability, and precision of the motor and its angle detecting system, the method using linear hall components to obtain motor rotor angle information is still a relatively appropriate solution. However, for achieving higher resolution precision of the rotor angle, the imperfect wave form of the output signal generated by the linear hall components needs to be modified to approximate to the actual rotor angle.